Hybrid and electric vehicles include a traction battery comprised of a number of cells. Traction batteries store energy and provide power to electric machines for propulsion and other functions. A battery control system may monitor the operation of the traction battery and may control the traction battery based on a variety of inputs. A useful value for the battery control system is the battery state of charge (SOC). Battery SOC is an estimate of the amount of energy remaining in the traction battery. The SOC may be derived from an integration of a battery current. Integration of the battery current requires the use of high accuracy current sensors because even small measurement errors will be integrated over a long period of time. It may be beneficial to determine SOC in an alternate way.